Co-combustion performance of coal with rice husks and bamboo

Biomass has been regarded as an important form of renewable energy due to the reduction of green house gas emission such as carbon dioxide. An experimental study of co-combustion of coal and biomass was performed in a laboratory-scale combustion facility. Rice husks and bamboo were the selected biomass fuels in this study due to their abundance in the Asia-Pacific region. Experimental parameters including the biomass blending ratio in the fuel mixture, relative moisture content and biomass grinding size were investigated. Both energy release data and pollutant emission information were obtained. Due to the decrease in the heating value from adding biomass in the fuel mixture, the combustion temperature and energy output from the co-firing process were reduced compared with coal combustion. On the other hand, gaseous pollutant emissions including carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx) and sulfur dioxide (SO2) were reduced and minimum energy-based emission factors were found in the range of 10–30% biomass blending ratio. With an increase in the moisture content in the biomass, decreases in combustion temperature, SO2, NOx and CO2 emissions were observed, while an increase in CO emissions was found. It has also been observed that chemical kinetics may play an important role compared to mass diffusion in the co-firing process and the change in biomass grinding size does not have much effect on the fuel burning rate and pollutant emissions under the current experimental conditions.